This invention relates to an improved coupler for detachably connecting a snowplow unit to a prime mover and, in particular, to an automatic device for safety locking the plow unit to the coupler.
As disclosed in U.S. Pat. No. 3,020,066, which issued in January 1959 to Torrey, coupling devices have been used for some time for attaching snowplow blades to a prime mover, such as a truck or the like, for the purpose of permitting rapid coupling and uncoupling of the blade unit. The coupling means is typically secured to the prime mover so that it can be driven against the push frame of the plow thereby causing a pair of spring-biased jaw elements associated with the coupler to automatically lock against a frame-mounted tongue that is forced therebetween. When in a locked condition, the jaw elements are seated within a pair of recessed shoulders formed in the tongue. The shoulders are contoured to draw the push frame snuggly against the front wall of the coupler.
Although most coupling devices of this type have proven to be a highly dependable means for connecting a plow unit to a prime mover, there are nevertheless times when, under severe operating conditions, the plow unit may be able to work itself free from the coupler. As the blade of the plow is driven over rough road surfaces or roads encrusted with ice, snow and sand, the equipment is subjected to serve vibrations and heavy multidirectional stresses. As a consequence, the biased jaw elements can be worked apart and foreign matter thrown up by the plow permitted to foul the coacting components. When this occurs, the jaws can be pushed back to a partially-opened position thereby allowing the plow unit to shift its position in reference to the coupler whereupon damage to the equipment will follow.